add 406 retry

Author: longbai

QiniuSDK/Http/QNResponseInfo.h

@@ -20,15 +20,14 @@ extern const int kQNNetworkError;
 @property (nonatomic, readonly, getter = isCancelled) BOOL canceled;
 @property (nonatomic, readonly, getter = isOK) BOOL ok;
 @property (nonatomic, readonly, getter = isConnectionBroken) BOOL broken;
+@property (nonatomic, readonly) BOOL couldRetry;
 
 + (instancetype)cancel;
 
 - (instancetype)initWithError:(NSError *)error;
 
 - (instancetype)initWithCancelled;
 
-@property (nonatomic, readonly) BOOL couldRetry;
-
 - (instancetype)init:(int)status
            withReqId:(NSString *)reqId
             withXLog:(NSString *)xlog

QiniuSDK/Http/QNResponseInfo.m

@@ -49,7 +49,7 @@ - (BOOL)isConnectionBroken {
 }
 
 - (BOOL)couldRetry {
-	return (_statusCode >= 500 && _statusCode < 600 && _statusCode != 579) || _statusCode == kQNNetworkError || _statusCode == 996;
+	return (_statusCode >= 500 && _statusCode < 600 && _statusCode != 579) || _statusCode == kQNNetworkError || _statusCode == 996 || _statusCode == 406;
 }
 
 - (instancetype)init:(int)status